<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <link rel="icon" href="favicon.ico" type="image/x-icon" />
    <title>Document</title>
    <style>
        .pane {
            width: 500px;
        }
        
        input {
            display: none;
        }
        
        input+label {
            display: block;
            width: 500px;
            line-height: 40px;
            background-color: #a9a9a9;
            border-top-left-radius: 5px;
            border-top-right-radius: 5px;
        }
        
        input+label+div {
            border: 1px solid #ccc;
            border-bottom-left-radius: 5px;
            border-bottom-right-radius: 5px;
            height: 0px;
            transition: .8s;
            overflow: hidden
        }
        
        .pane>div {
            margin-bottom: 5px;
        }
        
        input[type='radio']:checked+label+div {
            height: 150px;
        }
    </style>
</head>

<body>
    <div class='pane'>
        <div>
            <input type='radio' id='pane1' name='pane' checked>
            <label for='pane1'>点击我扩展。 再次点击我折叠。 Part I。</label>
            <div>
                Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat. Duis aute irure dolor
                in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum.
            </div>
        </div>
        <div>
            <input type='radio' id='pane2' name='pane'>
            <label for='pane2'>点击我扩展。 再次点击我折叠。 Part II。</label>
            <div>
                Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat. Duis aute irure dolor
                in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum.
            </div>
        </div>
        <div>
            <input type='radio' id='pane3' name='pane'>
            <label for='pane3'>点击我扩展。 再次点击我折叠。 Part  III。</label>
            <div>
                Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat. Duis aute irure dolor
                in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum.
            </div>
        </div>
    </div>
</body>

</html>